Memory system

ABSTRACT

A memory system includes a connector through which power for the memory system is to be supplied from an external device, a controller, a nonvolatile memory device, a power source circuit connected to the controller and the nonvolatile memory device by power lines through which power is supplied to the controller and the nonvolatile memory device, and a power source control circuit that receives a supply of power from the external device through the connector and supplies the power to the power control circuit. The power source control circuit is configured to detect using a divided voltage of a voltage of the power supplied thereto, that the voltage of the power supplied thereto is higher than a predetermined voltage and interrupt the power supplied to the power control circuit if the voltage of the power supplied thereto is higher than the predetermined voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-053937, filed Mar. 22, 2018, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a memory system.

BACKGROUND

In a memory system such as a solid state drive (SSD), an inputovervoltage protection circuit is integrated into a power source circuitreceiving input power.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a configuration of amemory system according to a first embodiment.

FIG. 2 is a block diagram schematically illustrating an example of aconfiguration of a power source control circuit according to the firstembodiment.

FIG. 3 is a diagram illustrating a first configuration example of thepower source control circuit according to the first embodiment.

FIG. 4 is a diagram illustrating a second configuration example of thepower source control circuit according to the first embodiment.

FIG. 5A is a diagram illustrating an example of a power source waveformat the time of a normal state in the memory system according to theembodiment, and FIG. 5B is a diagram illustrating an example of a powersource waveform at the time of an overvoltage state in the memory systemaccording to the embodiment.

FIG. 6 is a block diagram schematically illustrating an example of aconfiguration of a power source control circuit according to a secondembodiment.

DETAILED DESCRIPTION

Embodiments provide a memory system that protects a load from a highvoltage that is significantly above a standard voltage.

In general, according to one embodiment, a memory system includes aconnector through which power for the memory system is to be suppliedfrom an external device, a controller, a nonvolatile memory device, apower source circuit connected to the controller and the nonvolatilememory device by power lines through which power is supplied to thecontroller and the nonvolatile memory device, and a power source controlcircuit that receives a supply of power from the external device throughthe connector and supplies the power to the power control circuit. Thepower source control circuit is configured to detect using a dividedvoltage of a voltage of the power supplied thereto, that the voltage ofthe power supplied thereto is higher than a predetermined voltage andinterrupt the power supplied to the power control circuit if the voltageof the power supplied thereto is higher than the predetermined voltage.

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. In the following description,configuration elements having substantially the same functions andconfigurations are denoted by the same reference numerals or symbols,and repetitive description may be omitted.

FIG. 1 is a diagram illustrating an example of a configuration of amemory system 1 according to a first embodiment. Here, it is assumedthat the memory system 1 is implemented by an SSD that is used as a mainstorage of a host device 2. The memory system 1 is not limited to theSSD, and can be implemented by as various other types of a storage suchas a hybrid disk drive. The memory system 1 may be embedded in the hostdevice 2 or may be externally connected to the host device 2. Inaddition, a method of the present embodiment which will be describedbelow can be applied to not only a storage such as an SSD but alsovarious electronic devices.

The host device 2 is an information processing device such as a personalcomputer (PC) or a server. For example, PCI Express® (PCIe®) can be usedas an interface for interconnecting the memory system 1 and the hostdevice 2.

As illustrated in FIG. 1, the memory system 1 includes a controller 11,a volatile memory 12, a nonvolatile memory 13, a connector 14, a powersource circuit 15, and a power source control circuit 16.

The controller 11 receives a write or a read command from a host device2, writes data transferred from the host device 2 to the nonvolatilememory 13 in response to the write command, and reads data, which isrequested from the host device 2, from the nonvolatile memory 13 inresponse to the read command, while using the volatile memory 12 as acache. The controller 11 is, for example, a system on chip (SoC) inwhich a central processing unit (CPU) is embedded. A program for causingthe memory system 1 to perform a target operation is stored in apredetermined area of the nonvolatile memory 13. The program ispartially or entirely loaded into the volatile memory 12, for example,when the memory system 1 is activated, and is executed by the CPU in thecontroller 11.

The volatile memory 12 is, for example, a dynamic random access memory(RAM) (DRAM). In addition, the nonvolatile memory 13 is, for example, aNAND type flash memory. Here, it is assumed that the memory system 1includes the volatile memory 12, but a configuration without thevolatile memory 12 can also be assumed. For example, a configuration inwhich a storage corresponding to the volatile memory 12 is embedded inthe controller 11 can also be assumed.

The connector 14 has a shape conforming to, for example, the PCIestandard, and is a connection unit that connects the host device 2 tothe memory system 1. A read command, a write command, user data, and thelike from the host device 2 are transferred to the controller 11 via theconnector 14. In addition, user data read from the nonvolatile memory13, a response from the controller 11, or the like is transferred to thehost device 2 via the connector 14.

The power source circuit 15 is, for example, a power management IC(PMIC) that supplies power to each component (the controller 11, thevolatile memory 12, and the nonvolatile memory 13) in the memory system1 under the control of the controller 11. The power source circuit 15 isconnected to the host device 2 via the connector 14 and the power sourcecontrol circuit 16, and receives power from the host device 2. The powersource circuit 15 is connected to the controller 11, the volatile memory12 and the nonvolatile memory 13 by power source lines illustrated inFIG. 1, and can supply the power supplied from the host device 2 to thecontroller 11, the volatile memory 12, and the nonvolatile memory 13through these power source lines.

The power source control circuit 16 is interposed between the connector14 and the power source circuit 15. The power source control circuit 16is a control circuit for handling an overvoltage condition, inpreparation for an abnormal situation in which a voltage significantlyexceeding a rated voltage of the memory system 1 including the powersource circuit 15, is applied. For example, there is an erroneousinsertion of an AC adapter on the host device 2 side as a cause of theabnormal situation. If the voltage significantly exceeding the ratedvoltage of the power source circuit is applied, the power source circuitis damaged, and thereby, an input overvoltage protection circuit builtin the power source circuit does not operate. Thereby, it is impossibleto protect electronic circuits to which the power source circuitsupplies power.

The power source control circuit 16 adaptively disconnects the powersource line connecting the connector 14 to the power source circuit 15so as to protect the electronic circuits, more specifically, the powersource circuit 15 and each component (the controller 11, the volatilememory 12, and the nonvolatile memory 13) of the memory system 1. Thememory system 1 according to the present embodiment includes the powersource control circuit 16 that protects the electronic circuits from ahigh voltage that is significantly above a standard voltage.Hereinafter, the power source control circuit 16 will be described indetail.

FIG. 2 is a block diagram schematically illustrating an example of aconfiguration of the power source control circuit 16 according to thefirst embodiment.

As illustrated in FIG. 2, the power source control circuit 16 accordingto the present embodiment includes a switch unit (which is a switchcircuit) 161, a detection control unit (which is a logic circuit) 162,and a power source unit (which is a regulator circuit) 163.

The switch unit 161 switches ON/OFF states with respect to an inputpower a1 input from the host device 2 received via the connector 14. Theswitch unit 161 is normally in an ON state. In a case where the inputpower a1 is higher than a predetermined voltage, the switch unit 161 ischanged to the OFF state by a control output a4 received from thedetection control unit 162. In a case where a voltage of the input powera1 exceeds maximum rated voltages of each component in the power sourcecircuit 15 and the memory system 1, the switch unit 161 disconnects thepower source line with respect to a load before the voltage of the inputpower a1 reaches a value by which the power source circuit 15 and eachcomponent of the memory system 1 are damaged.

In order to detect an abnormality (e.g., a voltage higher than apredetermined voltage) of the power input from the host device 2, thedetection control unit 162 detects that a voltage obtained by dividingthe power input from the host device 2 exceeds a threshold value. Thedetection control unit 162 controls the switch unit according to adetection result. The detection control unit 162 receives the voltageobtained by dividing the input power a1 by resistors (a first resistorR2 and a second resistor R3) as a detection signal (a detection inputa3). The detection control unit 162 inverts an output (control outputa4) for the switch unit 161 before the voltage of the input powerreaches a value by which the power source circuit 15 and each componentof the memory system 1 are damaged, based on the detection input a3. Thethreshold value which is compared with the detection input a3 and servesas a reference value for inverting the control output a4 is set so as tocorrespond to a voltage value of the detection signal when a voltagevalue of the input power a1 reaches a value that can be determined to beabnormal.

Here, the detection input a3 that is input to the detection control unit162 is a voltage obtained by dividing the input power a1 by a resistor.Accordingly, by adjusting resistance values of the resistors R2 and R3,the voltage of the detection input a3 can be adjusted so as to beincluded within a certain range even in a case where the voltage of theinput power a1 significantly exceeds the rated voltage of the memorysystem 1.

The detection control unit 162 is a low voltage operation gate thatoperates even at a voltage lower than the rated voltage of the memorysystem 1. The detection control unit 162 needs to function before thepower source circuit 15 and each component of the memory system 1 startan operation. Accordingly, the power source unit 163 that supplies powerto the detection control unit 162 operates even at a voltage lower thanthe rated voltage of the memory system 1 and is not damaged even at avoltage significantly exceeding the rated voltage of the memory system1. A more detailed configuration of the power source unit 163 will bedescribed below.

Next, an operation of the power source control circuit 16 will bedescribed with reference to FIGS. 3 and 4. FIG. 3 is a diagramillustrating a first example configuration of the power source controlcircuit 16 according to the first embodiment. FIG. 4 is a diagramillustrating a second configuration example of the power source controlcircuit 16 according to the first embodiment.

In FIG. 3, the input power a1 is a power supplied from the host device 2side via the connector 14. The rated voltage (for example, +3.3 V) ofthe memory system 1 is supposed to be supplied as the input power a1. Inaddition, the control circuit power a2 is a power generated using theinput power a1 by the power source unit 163, and is a power used for anoperation of the detection control unit 162. The control circuit powera2 is set to a voltage lower than the rated voltage of the memory system1.

The power source unit 163 generates control circuit power a2 for anoperation of the detection control unit 162 using the power input fromthe host device 2. The power source unit 163 includes a constant voltagecircuit. For example, the constant voltage circuit includes an NPNtransistor Q3, a constant voltage element (e.g., Zener diode) D1, and aresistor R1 as illustrated in FIG. 3. In addition to this, the constantvoltage circuit can include a constant voltage element D2 and a resistorR7 as illustrated in FIG. 4.

The power source unit 163 generates a constant voltage of approximately2 V using the input power a1, and outputs the voltage as the controlcircuit power a2. That is, the power source unit 163 generates thecontrol circuit power a2. In addition, since the power source unit 163generates a constant voltage of approximately 2 V using a circuit havinga simple configuration, even if a voltage of the input power a1significantly exceeds the rated voltage of the memory system 1, thepower source unit is not damaged.

The detection control unit 162 includes an inverter G1 and resistors R2and R3. A voltage of the detection input a3 input to the inverter G1 isa voltage obtained by dividing the input power a1 by the resistors R2and R3. For example, in a case where the resistor R2 is 47 kΩ and theresistor R3 is 10 kΩ, if a supply voltage is 10 V, the detection inputa3 becomes 1.75 V. An output (control output a4) of the inverter G1 isset so as to be inverted (H→L) before the input power a1 reaches such avoltage that damages each component of the memory system 1. That is, ifa voltage value of the detection input a3 exceeds a threshold value, thedetection control unit 162 performs inversion (H→L) of the controloutput a4 in the inverter G1.

The switch unit 161 includes, for example, an FET Q1 and a controltransistor Q2. The switch unit 161 further includes resistors R4, R5,and R6. The FET Q1 is configured with, for example, a P-type MOS-FET.The control transistor Q2 receives control output a4 of the inverter G1(via the resistor R4) and switches ON/OFF states accordingly. The switchunit 161 switches the ON/OFF states with respect to the input power a1via the control transistor Q2.

The control transistor Q2 is, for example, an NPN transistor. In a casewhere the control transistor Q2 is an NPN transistor, when the controloutput a4 is H, the control transistor Q2 enters the ON state. Inaddition, in a case where the control transistor Q2 is an NPNtransistor, when the control output a4 is L, the control transistor Q2enters the OFF state.

In addition, the control transistor Q2 may be, for example, an N-typeMOS-FET instead of the NPN transistor. In a case where the controltransistor Q2 is an N-type MOS-FET, when the control output a4 is H, thecontrol transistor Q2 enters the ON state. In addition, in a case wherethe control transistor Q2 is an N-type MOS-FET, when the control outputa4 is L, the control transistor Q2 enters the OFF state.

In a case where the control transistor Q2 is turned on, the resistor R6is grounded and a gate voltage of the FET Q1 is lower than a voltage ofa source, and thereby, a source is connected to a drain. Thereby, theinput power a1 is supplied to the power source circuit 15 at asubsequent stage as a supply power a5. Accordingly, the switch unit 161enters an ON state.

In a case where the control transistor Q2 is turned off, the resistor R6is not grounded, and thereby, the gate and the source of the FET Q1 areat the same potential and the drain is disconnected from the source.Thereby, the input power a1 is not supplied to the power source circuit15 at the subsequent stage. That is, supplying the supply power a5 tothe power source circuit 15 is interrupted. Accordingly, the switch unit161 enters an OFF state.

In addition, the switch unit 161 may include other switch mechanisms inanother configuration, instead of the FET Q1 and the control transistorQ2. With the other switch mechanism, the switch unit 161 receives thecontrol output a4 of the inverter G1 and switches ON/OFF states withrespect to the input power a1 in accordance with the control output a4.

FIG. 5A is a diagram illustrating an example of a power source waveformat the time of a normal state in the memory system according to thefirst embodiment, and FIG. 5B is a diagram illustrating an example of apower source waveform at the time of an overvoltage state in the memorysystem according to the first embodiment. A vertical axis denotes avoltage and a horizontal axis denotes time. A vertical axis v1 indicatesa voltage at which the detection control unit 162 can operate, and v2indicates a rated voltage of the memory system. The labels t1 to t6 onthe horizontal axis denote time.

In a normal state, for example, in a case where the memory system 1 isan M.2 type SSD having a rated voltage of 3.3 V±5%, +3.3V which iswithin a rated voltage range is supplied as the input power a1, and inthe same manner, for example, in a case where the memory system 1 is a2.5 inch type SSD, +5 V which is within the rated voltage range issupplied as the input power a1. Meanwhile, when an overvoltage occurs,for example, in a case where the memory system 1 is an SSD of the formertype with the rated voltage of 3.3 V±5%, +5 V which is out of the ratedvoltage range is supplied as the input power a1, and in the same manner,for example, in a case where the memory system 1 is an SSD of the lattertype, +12 V which is out of the rated voltage range is supplied as theinput power a1.

As illustrated in FIG. 5A, in the normal state, a voltage value of theinput power a1 increases after the supplying is started, and a voltagevalue of the control circuit power a2 that is generated by using theinput power a1 also increases with a slight delay (t1 to t3). Voltagevalues of the detection input a3 (0 to t4), the control output a4 (t1 tot3), and the supply power a5 (t2 to t4) increase as the voltage value ofthe input power a1 increases. In addition, until the voltage value ofthe input power a1 increases up to the rated voltage (v2) of the memorysystem 1, the switch unit 161 is in the ON state (t2 to t4).

Before a voltage value of the input power a1 increases up to the ratedvoltage (v2) of the memory system 1, a constant voltage control of thecontrol circuit power a2 made by the power source unit 163 is completed(t3). Thereby, a stable operation of the detection control unit 162 isstarted. That is, the detection control unit 162 functions before thepower source circuit 15 and each component (the controller 11, thevolatile memory 12, and the nonvolatile memory 13) of the memory system1 start operations. If the detection input a3 obtained by dividing theinput power a1 does not exceed the threshold value, the detectioncontrol unit 162 does not perform an inversion (H→L) of the controloutput a4.

Thereafter, the voltage value of the control circuit power a2 is kept ata constant value (t3 to t4) even if the voltage value of the input powera1 continuously increases. If the voltage value of the input power a1increases up to the rated voltage (v2) of the memory system 1, thememory system stabilizes at the value (t4). Accordingly, the detectioninput a3 obtained by dividing the input power a1 does not exceed thethreshold value, and the detection control unit 162 does not perform theinversion (H→L) of the control signal a4. Thus, the switch unit 161 iskept in the ON state. As the result, supply power a5 to the power sourcecircuit 15 is maintained.

As illustrated in FIG. 5B, even when the overvoltage occurs, the voltagevalue of the input power a1 increases after the supplying is started,and the voltage value of the control circuit power a2 that is generatedby using the input power a1 also increases with a slight delay (t1 tot3), in the same manner as in the normal state. The voltage values ofthe detection input a3 (0 to t4), the control output a4 (t1 to t3), andthe supply power a5 (t2 to t4) increase as the voltage value of theinput power a1 increases. In addition, until the voltage value of theinput power a1 increases up to the rated voltage (v2) of the memorysystem 1, the switch unit 161 is in the ON state (t2 to t4).

In addition, even when the overvoltage occurs, the constant voltagecontrol of the control circuit power a2 made by the power source unit163 is completed (t3) before the voltage value of the input power a1increases up to the rated voltage (v2) of the memory system 1, in thesame manner as in the normal state.

Thereafter, the voltage value of the control circuit power a2 is kept ata constant value (t3 to t4) even if the voltage value of the input powera1 continuously increases.

Meanwhile, when the overvoltage occurs, the voltage value of the inputpower a1 continuously increases as it is (t4 to t6) even if the voltagevalue increases up to the rated voltage (v2) of the memory system 1,unlike the normal state. That is, the voltage value of the detectioninput a3 which is the voltage obtained by dividing the input power a1also continuously increases (t4 to t6). If the voltage value of thedetection input a3 exceeds the threshold value (t5), the detectioncontrol unit 162 performs the inversion (H→L) of the control output a4.Thus, the switch unit 161 changes to the OFF state. As the result, thesupply of power a5 to the power source circuit 15 is interrupted.

A voltage significantly exceeding the rated voltage of the power sourcecircuit 15 such that the power source circuit 15 is damaged may beprevented from being applied to the power source circuit 15 byinterrupting the supply of the supply power a5. That is, it is possibleto protect a load from a high voltage that is significantly above astandard voltage.

Furthermore, as illustrated in FIGS. 5A and 5B, the detection controlunit 162 operates at the voltage (v1) lower than the rated voltage (v2)of the memory system 1, and thus, control of the switch unit 161 maystart (t2) before the input power a1 reaches the rated voltage (v2) ofthe memory system 1.

In addition, as illustrated in FIG. 3, the input power a1 is divided bythe detection control unit 162 and is input to the inverter G1 in thedetection control unit 162 as the detection input a3. Accordingly, evenin a case where a voltage of the input power significantly exceeds therated voltage of the memory system 1, it is possible to adjust thedetection control unit 162 such that the detection control unit 162 isnot damaged.

In addition, as described above, the power source unit 163 is configuredso as not to be damaged even by a voltage significantly exceeding therated voltage of the memory system 1, and the detection control unit 162operates by using power generated by the power source unit 163configured in this way and the detection input a3 obtained by dividingthe input power a1. Accordingly, even if the voltage value of the inputpower a1 significantly exceeds, for example, the rated voltage of thememory system 1, there is no trouble in the operation of the detectioncontrol unit 162 in view of power.

As described above, the memory system 1 according to the embodimentprotects a load from a high voltage out of a standard.

FIG. 6 is a block diagram schematically illustrating an example of aconfiguration of the power source control circuit 16 according to asecond embodiment.

As illustrated in FIG. 6, the power source control circuit 16 accordingto the present embodiment includes the switch unit (which is a switchcircuit) 161 and the detection control unit (which is a logic circuit)162. The second embodiment is different from the first embodiment inthat the detection control unit 162 operates using another powersupplied from the outside of the power source control circuit 16.According to this, the power source unit 163 does not exist in thesecond embodiment.

According to the second embodiment, with such a configuration, there isno trouble in an operation of the detection control unit 162 thatoperates using the other power and the detection input a3 obtained bydividing the input power a1, even if the voltage value of the inputpower a1 significantly exceeds, for example, the rated voltage of thememory system 1. The other points are the same as in the firstembodiment.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A memory system comprising: a connector throughwhich first power for the memory system is to be supplied from anexternal device; a controller; a nonvolatile memory device; a powersource circuit connected to the controller by a first power line throughwhich power is supplied to the controller and connected to thenonvolatile memory device by a second power line through which power issupplied to the nonvolatile memory device; and a control circuitprovided between the connector and the power source circuit, wherein thecontrol circuit is configured to receive the first power through theconnector, detect that a divided voltage of a voltage of the receivedfirst power is higher than a threshold voltage, supply the first powerto the power source circuit if the divided voltage is lower than thethreshold voltage, and interrupt the first power from being supplied tothe power source circuit if the divided voltage is higher than thethreshold voltage.
 2. The memory system according to claim 1, whereinthe control circuit includes a power source unit configured to generatesecond power from the received first power; and a detection control unitconfigured to operate using the second power to detect that the dividedvoltage is higher than the threshold voltage.
 3. The memory systemaccording to claim 2, wherein the control circuit further includes aswitch element that is controlled on or off by a control output of thedetection control unit, the control output turning the switch element onif the divided voltage is lower than the threshold voltage and turningthe switch element off if the divided voltage is higher than thethreshold voltage.
 4. The memory system according to claim 2, whereinthe detection control unit comprises a resistor for generating thedivided voltage to generate a detection signal.
 5. The memory systemaccording to claim 4, wherein, in a case where a voltage value of thedetection signal exceeds a threshold value, the detection control unitcontrols the switch element to turn off.
 6. The memory system accordingto claim 5, wherein, when a voltage value of the first power reaches avalue that is capable of being determined to be abnormal, the voltagevalue of the detection signal corresponds to the threshold value.
 7. Thememory system according to claim 6, wherein the detection control unitcomprises a gate that inverts an output in a case where the voltagevalue of the detection signal exceeds the threshold value.
 8. The memorysystem according to claim 2, wherein the power source unit is configuredto generate the second power by a circuit which includes at least aconstant voltage element and a resistor, and which produces a constantvoltage.
 9. The memory system according to claim 3, wherein the switchelement comprises a P-type MOS-FET that is turned on or off according tothe control output.
 10. The memory system according to claim 1, whereinthe power source circuit is configured to generate operation power foreach component of the memory system including the controller and thenonvolatile memory device, using the first power.